Chernobyl disaster The worst manmade disaster in human history Czech Technical University In Prague 23 May 2007

Czech Technical University in Prague2 Where is Chernobyl?

23 May 2007Czech Technical University in Prague3 Chernobyl Built in Built in ChornobylChornobyl

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23 May 2007Czech Technical University in Prague5 Background Reaktor Bolshoy Moshehnosty KipyashiyReaktor Bolshoy Moshehnosty Kipyashiy RBMK, a Russian acronym translated roughly means “reactor (of) high power (of the) channel (type)”RBMK, a Russian acronym translated roughly means “reactor (of) high power (of the) channel (type)” reactor cooled by water and moderated by graphitereactor cooled by water and moderated by graphite

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23 May 2007Czech Technical University in Prague7 RBMK Reactor

23 May 2007Czech Technical University in Prague8 Fuel assemblies

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23 May 2007Czech Technical University in Prague10 Reactor Plant Scenario 1.As the reaction occurs, the uranium fuel becomes hot 2.The water pumped through the core in pressure tubes removes the heat from the fuel 3.The water is then boiled into steam 4.The steam turns the turbines 5.The water is then cooled 6.Then the process repeats

23 May 2007Czech Technical University in Prague11 Day of disaster 25 April :00 The preparation for the test01:00 The preparation for the test 13:47 Lowering of the reactor power halted at 1,600 MWt13:47 Lowering of the reactor power halted at 1,600 MWt 14:00 The ECCS was isolated14:00 The ECCS was isolated 23:10 The power reduction resumed23:10 The power reduction resumed

23 May 2007Czech Technical University in Prague12 26 April :00 Operation shift change24:00 Operation shift change 24:28 Power level is now 500 MWt and kept decreasing to 30 MWt24:28 Power level is now 500 MWt and kept decreasing to 30 MWt 24:40 The operator withdrew some control rods24:40 The operator withdrew some control rods 01:00 Power had risen to 200 MWt01:00 Power had risen to 200 MWt 01:03 Connecting the fourth main cooling pump to the left loop of the system 200 MWt01:03 Connecting the fourth main cooling pump to the left loop of the system 200 MWt 01:07 Connecting the fourth main cooling pump to the right of the loop system - this was a violation of NOP01:07 Connecting the fourth main cooling pump to the right of the loop system - this was a violation of NOP

23 May 2007Czech Technical University in Prague13 26 April 1986 (cont.) 01:19 Increased feed water flow to the steam drums and removed more control rods -violation of NOP01:19 Increased feed water flow to the steam drums and removed more control rods -violation of NOP 01:23 The test was started01:23 The test was started 01:23:10 Automatic rods withdrawn from the core01:23:10 Automatic rods withdrawn from the core 01:23:21 Two groups of automated control rods were back to the core01:23:21 Two groups of automated control rods were back to the core

23 May 2007Czech Technical University in Prague14 26 April 1986 (cont.) 01:23:30 Power kept increasing01:23:30 Power kept increasing 01:23:40 Emergency button pushed01:23:40 Emergency button pushed 01:23:44 Power is at MWth01:23:44 Power is at MWth 01:23:48 1 st thermal explosion01:23:48 1 st thermal explosion 01:23:55 2 nd explosion01:23:55 2 nd explosion

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23 May 2007Czech Technical University in Prague18 Human Errors Isolation of the emergency core cooling systemIsolation of the emergency core cooling system Unsafe amount of control rods withdrawnUnsafe amount of control rods withdrawn Connection of the four main cooling pumps to the right and left of the systemConnection of the four main cooling pumps to the right and left of the system

23 May 2007Czech Technical University in Prague19 Human Errors (cont.) Mental modelMental model –The operator did not have a good mental model of the system itself OverconfidenceOverconfidence –By having an electrical engineer on site for an electrical test –No confirmation of cues obtained from the system Beta too highBeta too high –Many missed signals before the accident

23 May 2007Czech Technical University in Prague20 Accident Prevention

23 May 2007Czech Technical University in Prague21 System Analysis Use of graphite as a moderatorUse of graphite as a moderator Lack of a well-built containment structureLack of a well-built containment structure Inadequate instrumentation and alarms for an emergency situationInadequate instrumentation and alarms for an emergency situation There were no physical controls that prevented the operators from operating the reactor in its unstable stateThere were no physical controls that prevented the operators from operating the reactor in its unstable state

23 May 2007Czech Technical University in Prague22 Summary of Facts April 26, 1986:April 26, 1986: –Chernobyl nuclear power plant Operator errors cause a reactor explosionOperator errors cause a reactor explosion Explosion releases 190 tons of radioactive gasses into the atmosphereExplosion releases 190 tons of radioactive gasses into the atmosphere Fire starts that lasts 10 daysFire starts that lasts 10 days People:People: –7 million lived in contaminated areas; 3 million were children Wind:Wind: –Carries radiation far distances

23 May 2007Czech Technical University in Prague23 Far Reaching Radiation

23 May 2007Czech Technical University in Prague24 Radioactive fallout

23 May 2007Czech Technical University in Prague25 Direct Casualties 5.5 million people still live in contaminated areas5.5 million people still live in contaminated areas 31 people died in 3 months of radiation poisoning31 people died in 3 months of radiation poisoning 134 emergency workers suffered from acute radiation sickness134 emergency workers suffered from acute radiation sickness 25,000 rescue workers died since then of diseases caused by radiation25,000 rescue workers died since then of diseases caused by radiation Cancer afflicts many othersCancer afflicts many others Increased birth defects, miscarriages, and stillbirthsIncreased birth defects, miscarriages, and stillbirths

23 May 2007Czech Technical University in Prague26 Indirect Casualties –By the year 2000 there were 1800 case of thyroid cancer in children and adolescent –High number of suicide and violent death among Firemen, policemen, and other recovery workers

23 May 2007Czech Technical University in Prague27 Environment Impact Areas still impacted today:Areas still impacted today: –Soil –Ground Water –Air –Food CropsCrops LivestockLivestock

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23 May 2007Czech Technical University in Prague33 Problems Today The SarcophagusThe Sarcophagus –After the disaster, a huge cement box was built around the radioactive material –It is falling apart! –According to a 2003 report by the Russian Atomic Energy Minister, Alexander Rumyantsev, "the concrete shell surrounding the Chernobyl nuclear reactor is in real danger of collapsing at any time." –A new Sarcophagus is scheduled to be completed in 2009

23 May 2007Czech Technical University in Prague34 Recommendations Have proper Standard Operating Procedures (SOP) for both normal and emergency situationsHave proper Standard Operating Procedures (SOP) for both normal and emergency situations Have scheduled trainings and practices for normal and emergency situationsHave scheduled trainings and practices for normal and emergency situations

23 May 2007Czech Technical University in Prague35 Recommendations (cont.) Always have a reactor expert on siteAlways have a reactor expert on site Have operators confirm any cues from the system before making hypothesis or take actionHave operators confirm any cues from the system before making hypothesis or take action Have a team work kind of environment such that every body is involvedHave a team work kind of environment such that every body is involved

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